Programmable links are electrical interconnects that are broken or created at selected electronic Bodes to activate or deactivate the selected electronic nodes. The activation/deactivation of the selected electronic interconnects may be performed by a user after an integrated circuit is fabricated and packaged. The combination of activated and deactivated electronic interconnects represents a digital bit pattern signifying data the user wishes to store.
In recent years, another type of programmable link, called an anti-fuse link, has been developed for use in integrated circuit applications. Instead of the programming mechanism causing an open circuit, as is the case with fusible links, the programming mechanism in anti-fuse circuits creates short circuit or a relatively low resistance link. Anti-fuse links consist of two conductor and/or semiconductor materials having a dielectric or insulating material between the conductive materials. During programming, the dielectric at selected points in between the conductive materials is broken down by predetermined applied voltages, thereby electrically connecting the conducting or semiconducting materials together.
The anti-fuse device can be integrated into a semiconductor memory cell having a data storage element constructed around an ultra-thin dielectric, such as agate oxide. The anti-fuse device can be implemented to store information by stressing a dielectric into breakdown (soft or hard breakdown) to set a leakage current level of the memory cell. The memory cell is read by sensing the current drawn by the cell.
Recent growth in the use of anti-fuse devices to provide read-only memory cells is being driven by an increased demand for secure computing. In particular, digital security applications, for example, specify a large number of encrypted, programmable read only memory cells. Unfortunately, standard anti-fuse manufacturing generally specifies the use of several mask, deposition or etching steps during or after the formation of the anti-fuse, thus increasing the fabrication complexity and cost of an integrated circuit.